In general terms, the present invention relates to the production of polyurethane foam by mixing an isocyanate with a polyalcohol, particularly a polyol.
In industry, such polyurethane foams are generally produced by a machine having two components with two separate tanks ensuring the dosing of the starting products with the aid of high pressure positive displacement pumps. Such apparatuses, which are well suited to heavy installations for continuous production, have a relatively long operating time and do not very satisfactorily solve the problem of the fast production of a large amount of polyurethane foam at the place where it will be used, particularly due to the weight and overall dimensions required, which are incompatible with the construction of a portable system.
Other means for realizing the basic starting product for a polyurethane foam have been designed, such as low pressure mixing using a mechanical stirrer, e.g. an immersed propeller, downstream of a volumetric dosing system. However, such an apparatus is relatively complex, if its operation is to be made automatic and reliable at any location where an intervention is necessary.
It has been found that it is possible to use the fast, in situ production of large amounts of polyurethane foam for protecting precious objects, such as those located in banks and in safes within the latter by rapidly concealing them in such a foam, which constitutes a dissuasive, impenetrable envelope for third parties wishing to steal such objects.